Hall sensors are often used to measure distance and/or changes in position in applications requiring a high degree of precision with regard to the measurements.
While hall sensors can be used to make measurements to a high degree of precision, the mechanical relationship between elements may allow for a certain amount of what is referred to as free play between elements in the system. In many cases, especially where components are left relatively loose to minimize friction and thus the amount of force required to move an object, the accuracy of measurement made possible by use of a hall sensor may be greater than the reliability of the mechanical system to maintain a consistent position, e.g., relative to a sidewall of a mount.
In compact systems such as cameras there is often a desire to keep components small, light and/or low power for a variety of reasons. For this reason, it is desirable to use small compact motors or drive devices to move components given the size and low power consumption advantages of such devices. To allow a small motor or drive device to move a mirror or other device it is often desirable to have little friction at the location of a hinge or moveable shaft used to mount the mirror or other component. To have low friction a loose fit may be used between the shaft and the support in which the shaft is mounted.
In the case of camera components high accuracy is required in terms of detecting and/or controlling the position of a moveable component such as a mirror.
In the case of mirrors supported using loose shafts, rather than simply rotate in a desired direction, there may be a side to side movement as the shaft mounted component and/or shaft slide side to side in a mount as the supported component is moved, e.g., rotated, about the shaft axis. In the case where a distance sensor is used to measure a distance to the mirror from which the angle of the mirror is determined, such side to side motion, although slight, can introduce minor errors into the estimate of the mirror position relative to a fixed sensor. This can cause a loss in accuracy in determining the angle of the mirror from such a distance measurement.
In some camera systems the side to side motion of a mounted mirror can introduce an error in the estimate of the angle of the mirror by one or two percent or some other amount. Such an error can have a significant impact on the control of the mirror position making it difficult to control the position of the mirror to as high a degree of accuracy as might be desirable in at least some camera applications.
While mirror position measurement and control is one example in which a hall sensor is used, and side to side motion may introduce errors, similar problems may and will occur in other applications where a hall sensor is used and undesired side to side motion of an object to which a distance is being measured may occur, e.g., due to an intentionally loose shaft or other mounting component.
In view of the above, it should be appreciated that there is a need for improved methods and/or apparatus which would allow for accurate measuring, maintaining and/or adjusting of a position of a moveable mounted component, e.g., a shaft mounted component, while still allowing for a relatively low friction mounting arrangement.